High resistance electrode



I Patented, May 3i),v 1939 UNITED STATES men Basis-rapes amt-moon Franz B. Hensel, Indianapolis, Ind, assign P. B. Mallory & Co. Inc.,

or to lndianawl l, Indy a corporation of Delaware No Drawing. Application October 5. 19 37, 1 Serial No. 167,371 a a Claims. .(cl. ale-4) This invention relates to electrodes of the type used 4 for electric upsetting, resistance welding and the like.

Objects of the invention are to improve the 5 characteristics and composition of such electrodes. g

Other objects of the invention will be apparent from the following description taken in connection with the appended claims. I

The present invention comprises the combination of elements, methods of manufacture, and theproduct thereof brought out and exemplified in the disclosure hereinafter set forth, the scope of the invention being indicated in the appended 4 While a preferred embodiment of the invention is described herein, itis contemplated that considerable variation may be made in themethod of procedure and the combination of elements 20 without departing from the spirit of the inven-' tion. .The invention contemplates the production of electrodes, such as welding and upsetting electrodes and dies characterized by an electrical conductivity of not greater than 10% of that of pure copper and composed of a sintered composition of a refractory metal or refractory compound interspersed with a low conductivity metal or alloy of lower melting point.

The prior art shows electrodes formed of metalso he compositions comprising refractory metals such as tungsten, molybdenum or their carbides sintered together and impregnated, with soft malleable highly conductive metals such as silver, copper or their highly conductive alloys. In such as cases, it has always been an object to produce an electrode of high electrical conductivity. I have now discovered that unexpected advantages may be obtained in many applications by impregnating sintered refractory materials with a high re- 0 sistance metal or alloy such that the conductivity of the completed product does not exceed 10% that of pure copper. I have found that .I can obtain the desired compositions by substituting for the impregnating metals previously used,

metal alloys such as copper-nickel, copper manganese, etc., the proportions of the elements so borides of the metals of titanium, zirconium, hafnium, vanadium, columbium and tantalum. l br the lower melting point alloys, I prefer copper base materials, and I have had great success with copper-manganese alloys of the composition copper and 30% manganese, or copper-nickel alloys. The materials which are being used should preferably have an electrical resistivity of not less than 30 microhms per cubic centimeter. In some cases, however, I may use alloys with resistivities below that value which have a tendency to alloy directly with the tungsten or other refractory material, and therefore form a solid solution which brings the conductivity of the finished product down to the desired value. In general, copper alloys containing 10, to of nickel and/or manganese are preferred.

The electrical conductivity of the metal composition descrlbed, shouldbe below 10% ofthe conductivity oi annealed copper and it may preferably be below 5% of the conductivity of standard annealed copper.

A method which I have found to be particularly successful, is to mix'50% tungsten and 50% tungsten carbide until a very intimate mixture is obtained. This mixture is then pressed and sintered at a temperature of approximately 1250 degrees C. After this sinterlng operation the material can be alloyed directly, or it maybe broken up again and re-pressed or the sintered product might be subjected to some mechanical working and to a subsequent 're-sintering. After any meet these steps shall have been carried" out,

modulus of rupture is about 150,000 pounds p. s. i.,

and the electrical conductivity, is less than 5% and usually inthe neighborhood of 3 to 4%. The fracture of the material prepared in the above described manner shows that the material is completely alioyed-aud of fine texture and of great uniformity. I have foundthat the material can be machined-to the shapedesired.

If. ch a metal is used as an upsetting die it will ct away the heat from the piece which is heated but will keep it'there in order to facilitate the upsetting operation. In addition heat will be generated in the electrode itself to aid in the upsetting operation. It will furthermore have many times the life of other materials which do not have this type of composition. Most straight alloys of low conductivity, without the refractory base, will soften at elevated temperatures, such as 500-800 degrees C., while tungsten and carbidic materials will not be afiected at such temperature ranges.

If a higher electrical conductivity is allowable, such as approximately 10% of that of pure annealed copper, I have found it possible to produce such a material by taking a mixture of 95% tungsten and 5% copper. This mixture is pressed and sintered. After sintering, the bars are impregnated at a temperature of 1300 to 1400 de-- grees C. with an alloy containing 30% nickel and 70% copper. Such a material will have a finished density of almost 14 grams per cubic cen-- timeter, and it will have a Rockwell B hardness of over 100 and a modulus of rupture of 195,000 p. s. i. and a high degree of deformation, which is an indication of great toughness of the material. when fracturing such material, it was found that a uniform and complete absorption had occurred.

By using manganese-copper instead of coppernickel, similar results are obtained, but I have found that the addition of nickel in most cases in substantial quantities and preferably above 2% is very beneficial. A finished composition containing approximately 5% nickel and more than 5% manganest is especially desirable.

I have not found it necessary to add any material which will improve the impregnating characteristics, because in all of my work I have never found that nonhomogeneous material is obtained by using either a copper-nickel or a copper-manganese or a coppel-nickel-manganese alloy. It is not necessary to add silicon to the composition, but on the other hand silicon will not change the properties materially and impurities of silicon therefore are not considered objectionable. Some other impurities or additives may, of course, also be present where they do not materially change the characteristics. I

While the present invention,'as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. A high resistance electrode of the type suitable for resistance welding and electric upsetting, said electrode having an electrical conductivity not greater than of that of pure copper, this electrode being formed of a metallic composition consisting of a refractory material selected from the group consisting of the refractory metals and refractory metal compounds intimately mixed and alloyed with a lower melting point alloy of copper and a metal calculated to materially reduce the electrical conductivity thereof, the pro.- portions of the ingredients being such thatv the electrical conductivity of the composition is less than 10% of that of pure copper and thematerial has high strength and hardness at room and. elevated temperatures.

2. A high resistance electrode of the type suitable for resistance welding and electric upsetting, said electrode having an electrical conductivity not greater than 10% of that of pure copper, the electrode being formed of a metallic composition consisting of a refractory material selected from the group consisting of the refractory metals and refractroy metal compounds intimately mixed and alloyed with a lower melting point alloy of copper and 10 to 75% ofmetal selected from the group consisting of nickel and manganese.

3. A high resistance electrode of the type suitable for resistance welding and electric upsetting, said electrode being formed of a metal composition consisting of about tungsten, 30% tungsten carbide, 28% copper and 12% nickel.

4. A high resistance electrode of the type suitable for resistance welding and electric upsetting, said electrode being former of a metal composition consisting of a mass of particles of refractory material selected from the refractory metals and their carbides impregnated with a high resistance copper alloy containing 10 to 75% of a metal selected from the group consisting of nickel and manganese.

5. A high resistanace electrode of the type suitable for resistance welding and electric upsetting, said electrode being formed of a sintered mixture of refractory metal selected from the group consisting of tungsten, molybdenum and chromium with refractory metal compound selected from the carbides, nitrides and borides of metalsttaken fnom the fourth and fifth groups of the periodic system and the carbides of tungsten and molybdenum, said sintered mixture being interspersed and bonded with a copper alloy of high electrical resistivity, said electrode being characterized by high hardness and mechanical strength at room and elevated temperatures.

FRANZ R. HENSEL. 

